Abstract

Microcosm studies in the laboratory demonstrate that sufficient dosages of wastewater effluent (microbial inoculum) and returned milk (substrate) can effectively raise the pH of pyrite-amended acid mine drainage water to circumneutral levels under aerobic conditions in as little as 7 days, and the pH remains at these levels for >19 months. Microbial analysis indicates that a complex biofilm (>70 species) forms over the pyrite. The biofilm dominantly consists of facultative anaerobes, which potentially interact with obligate anaerobes, such as sulfate-reducing Desulfosporosinus sp., to maintain an oxygen-free micro-environment surrounding the pyrite, even though the overlying water remains aerobic. The biofilm became established in water samples with an initial pH as low as 2, and subsequently caused the water pH to increase to circumneutral levels. Concurrently, concentrations of Al, As, Cu, Fe, Pb, Ni, and Zn all decreased substantially compared to baseline concentrations in the control microcosms.

Notes

Acknowledgments

The authors thank Dr. Terry Brown (Western Research Institute) for his technical advice, Dr. Amy Pruden (Colorado State University) for assistance in microbial analysis, and Jeff Cooper, Joel Mason, and Jesse Newcomer (Western Research Institute) for assistance with this project. This research was conducted and supported by Western Research Institute (WRI) and Kennecott Energy. Financial support was provided by the U.S. Dept of Energy (DoE) through Western Research Institute’s Cooperative Agreement DE-FC26-98FT40322 with DoE and Kennecott Energy. Any opinions, findings, conclusions, or recommendations expressed herein are those of the authors and do not reflect the view of the DoE or Kennecott Energy.